Chosen Solution
Hello! i have a slight problem with my MacBook Pro early 2015. For some reason the keyboard strokes are not correctly registered by the OS. On the login screen typing either triggers the “can’t type here” sound or wrong letters / erratic movement occur. For example pressing the louder button usually first turns the sound down twice and then mutes the Mac. Also a trackpad click only triggers the secondary function. A normal click or tap is not possible. This is already weird but I also checked the onscreen keyboard and there the right buttons are highlighted meaning that at least there I see full function . However, After connecting an external keyboard and typing a little bit the onscreen keyboard shows only weird signs when I type one the MacBooks keyboard Sometimes the keyboard completely works for some time just to revert to the no-function a little later. What did I try to fix it: I already exchanged the cable that connects the trackpad to the logic board and cleared the nvram.
I had to replace the top case. There was some water damage to the keyboard. This fixed the problem
If you’ve already replaced the trackpad cable and you’re still experiencing these problems, then the next in line would be the trackpad itself. I’d go ahead and replace it and see if it corrects your problem.
